and with insufficient paranoia in code that follows t_ctid links.
This patch covers the 7.3 branch.
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.149.2.1 2004/10/13 22:22:21 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.149.2.2 2005/08/26 20:07:15 tgl Exp $
*
*
* INTERFACE ROUTINES
/*
* heap_get_latest_tid - get the latest tid of a specified tuple
+ *
+ * Actually, this gets the latest version that is visible according to
+ * the passed snapshot. You can pass SnapshotDirty to get the very latest,
+ * possibly uncommitted version.
+ *
+ * *tid is both an input and an output parameter: it is updated to
+ * show the latest version of the row. Note that it will not be changed
+ * if no version of the row passes the snapshot test.
*/
-ItemPointer
+void
heap_get_latest_tid(Relation relation,
Snapshot snapshot,
ItemPointer tid)
{
- ItemId lp = NULL;
- Buffer buffer;
- PageHeader dp;
- OffsetNumber offnum;
- HeapTupleData tp;
- HeapTupleHeader t_data;
+ BlockNumber blk;
ItemPointerData ctid;
- bool invalidBlock,
- linkend,
- valid;
+ TransactionId priorXmax;
+
+ /* this is to avoid Assert failures on bad input */
+ if (!ItemPointerIsValid(tid))
+ return;
/*
- * get the buffer from the relation descriptor Note that this does a
- * buffer pin.
+ * Since this can be called with user-supplied TID, don't trust the
+ * input too much. (RelationGetNumberOfBlocks is an expensive check,
+ * so we don't check t_ctid links again this way. Note that it would
+ * not do to call it just once and save the result, either.)
*/
-
- buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
-
- if (!BufferIsValid(buffer))
- elog(ERROR, "heap_get_latest_tid: %s relation: ReadBuffer(%lx) failed",
- RelationGetRelationName(relation), (long) tid);
-
- LockBuffer(buffer, BUFFER_LOCK_SHARE);
+ blk = ItemPointerGetBlockNumber(tid);
+ if (blk >= RelationGetNumberOfBlocks(relation))
+ elog(ERROR, "block number %u is out of range for relation \"%s\"",
+ blk, RelationGetRelationName(relation));
/*
- * get the item line pointer corresponding to the requested tid
+ * Loop to chase down t_ctid links. At top of loop, ctid is the
+ * tuple we need to examine, and *tid is the TID we will return if
+ * ctid turns out to be bogus.
+ *
+ * Note that we will loop until we reach the end of the t_ctid chain.
+ * Depending on the snapshot passed, there might be at most one visible
+ * version of the row, but we don't try to optimize for that.
*/
- dp = (PageHeader) BufferGetPage(buffer);
- offnum = ItemPointerGetOffsetNumber(tid);
- invalidBlock = true;
- if (!PageIsNew(dp))
- {
- lp = PageGetItemId(dp, offnum);
- if (ItemIdIsUsed(lp))
- invalidBlock = false;
- }
- if (invalidBlock)
+ ctid = *tid;
+ priorXmax = InvalidTransactionId; /* cannot check first XMIN */
+ for (;;)
{
- LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
- ReleaseBuffer(buffer);
- return NULL;
- }
+ Buffer buffer;
+ PageHeader dp;
+ OffsetNumber offnum;
+ ItemId lp;
+ HeapTupleData tp;
+ bool valid;
- /*
- * more sanity checks
- */
+ /*
+ * Read, pin, and lock the page.
+ */
+ buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid));
- tp.t_datamcxt = NULL;
- t_data = tp.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
- tp.t_len = ItemIdGetLength(lp);
- tp.t_self = *tid;
- ctid = tp.t_data->t_ctid;
+ if (!BufferIsValid(buffer))
+ elog(ERROR, "ReadBuffer(\"%s\", %lu) failed",
+ RelationGetRelationName(relation),
+ (unsigned long) ItemPointerGetBlockNumber(&ctid));
- /*
- * check time qualification of tid
- */
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
+ dp = (PageHeader) BufferGetPage(buffer);
- HeapTupleSatisfies(&tp, relation, buffer, dp,
- snapshot, 0, (ScanKey) NULL, valid);
+ /*
+ * Check for bogus item number. This is not treated as an error
+ * condition because it can happen while following a t_ctid link.
+ * We just assume that the prior tid is OK and return it unchanged.
+ */
+ offnum = ItemPointerGetOffsetNumber(&ctid);
+ if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
+ lp = PageGetItemId(dp, offnum);
+ if (!ItemIdIsUsed(lp))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- linkend = true;
- if ((t_data->t_infomask & HEAP_XMIN_COMMITTED) != 0 &&
- !ItemPointerEquals(tid, &ctid))
- linkend = false;
+ /* OK to access the tuple */
+ tp.t_self = ctid;
+ tp.t_datamcxt = NULL;
+ tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+ tp.t_len = ItemIdGetLength(lp);
- LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
- ReleaseBuffer(buffer);
+ /*
+ * After following a t_ctid link, we might arrive at an unrelated
+ * tuple. Check for XMIN match.
+ */
+ if (TransactionIdIsValid(priorXmax) &&
+ !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data)))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- if (!valid)
- {
- if (linkend)
- return NULL;
- heap_get_latest_tid(relation, snapshot, &ctid);
- *tid = ctid;
- }
+ /*
+ * Check time qualification of tuple; if visible, set it as the new
+ * result candidate.
+ */
+ HeapTupleSatisfies(&tp, relation, buffer, dp,
+ snapshot, 0, NULL, valid);
+ if (valid)
+ *tid = ctid;
+
+ /*
+ * If there's a valid t_ctid link, follow it, else we're done.
+ */
+ if ((tp.t_data->t_infomask & (HEAP_XMAX_INVALID |
+ HEAP_MARKED_FOR_UPDATE)) ||
+ ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- return tid;
+ ctid = tp.t_data->t_ctid;
+ priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ } /* end of loop */
}
/*
*/
int
heap_delete(Relation relation, ItemPointer tid,
- ItemPointer ctid, CommandId cid)
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid)
{
ItemId lp;
HeapTupleData tp;
dp = (PageHeader) BufferGetPage(buffer);
lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+
tp.t_datamcxt = NULL;
- tp.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
+ tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
tp.t_len = ItemIdGetLength(lp);
tp.t_self = *tid;
- tp.t_tableOid = relation->rd_id;
l1:
sv_infomask = tp.t_data->t_infomask;
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated);
+ Assert(!(tp.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = tp.t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(tp.t_data);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
return result;
void
simple_heap_delete(Relation relation, ItemPointer tid)
{
- ItemPointerData ctid;
int result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
- result = heap_delete(relation, tid, &ctid, GetCurrentCommandId());
+ result = heap_delete(relation, tid,
+ &update_ctid, &update_xmax,
+ GetCurrentCommandId());
switch (result)
{
case HeapTupleSelfUpdated:
*/
int
heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
- ItemPointer ctid, CommandId cid)
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid)
{
ItemId lp;
HeapTupleData oldtup;
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated);
+ Assert(!(oldtup.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = oldtup.t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(oldtup.t_data);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
return result;
void
simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
{
- ItemPointerData ctid;
int result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
- result = heap_update(relation, otid, tup, &ctid, GetCurrentCommandId());
+ result = heap_update(relation, otid, tup,
+ &update_ctid, &update_xmax,
+ GetCurrentCommandId());
switch (result)
{
case HeapTupleSelfUpdated:
/*
* heap_mark4update - mark a tuple for update
+ *
+ * Note that this acquires a buffer pin, which the caller must release.
+ *
+ * Input parameters:
+ * relation: relation containing tuple (caller must hold suitable lock)
+ * tuple->t_self: TID of tuple to lock (rest of struct need not be valid)
+ * cid: current command ID (used for visibility test, and stored into
+ * tuple's cmax if lock is successful)
+ *
+ * Output parameters:
+ * *tuple: all fields filled in
+ * *buffer: set to buffer holding tuple (pinned but not locked at exit)
+ * *ctid: set to tuple's t_ctid, but only in failure cases
+ * *update_xmax: set to tuple's xmax, but only in failure cases
+ *
+ * Function result may be:
+ * HeapTupleMayBeUpdated: lock was successfully acquired
+ * HeapTupleSelfUpdated: lock failed because tuple updated by self
+ * HeapTupleUpdated: lock failed because tuple updated by other xact
+ *
+ * In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
+ * If t_ctid is the same as t_self, the tuple was deleted; if different, the
+ * tuple was updated, and t_ctid is the location of the replacement tuple.
+ * (t_xmax is needed to verify that the replacement tuple matches.)
*/
int
heap_mark4update(Relation relation, HeapTuple tuple, Buffer *buffer,
+ ItemPointer ctid, TransactionId *update_xmax,
CommandId cid)
{
ItemPointer tid = &(tuple->t_self);
dp = (PageHeader) BufferGetPage(*buffer);
lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+ Assert(ItemIdIsUsed(lp));
+
tuple->t_datamcxt = NULL;
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tuple->t_len = ItemIdGetLength(lp);
+ tuple->t_tableOid = RelationGetRelid(relation);
l3:
sv_infomask = tuple->t_data->t_infomask;
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated);
- tuple->t_self = tuple->t_data->t_ctid;
+ Assert(!(tuple->t_data->t_infomask & HEAP_XMAX_INVALID));
+ *ctid = tuple->t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(tuple->t_data);
LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
return result;
}
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.136.2.2 2003/05/19 17:23:54 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.136.2.3 2005/08/26 20:07:15 tgl Exp $
*
*-------------------------------------------------------------------------
*/
if (newSlot != NULL)
{
int test;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
+
+ *newSlot = NULL;
/*
* mark tuple for update
*/
- *newSlot = NULL;
- tuple.t_self = *tid;
ltrmark:;
- test = heap_mark4update(relation, &tuple, &buffer, cid);
+ tuple.t_self = *tid;
+ test = heap_mark4update(relation, &tuple, &buffer,
+ &update_ctid, &update_xmax, cid);
switch (test)
{
case HeapTupleSelfUpdated:
ReleaseBuffer(buffer);
if (XactIsoLevel == XACT_SERIALIZABLE)
elog(ERROR, "Can't serialize access due to concurrent update");
- else if (!(ItemPointerEquals(&(tuple.t_self), tid)))
+ else if (!ItemPointerEquals(&update_ctid, &tuple.t_self))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- relinfo->ri_RangeTableIndex,
- &(tuple.t_self));
-
- if (!(TupIsNull(epqslot)))
+ /* it was updated, so look at the updated version */
+ TupleTableSlot *epqslot;
+
+ epqslot = EvalPlanQual(estate,
+ relinfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
+ if (!TupIsNull(epqslot))
{
- *tid = tuple.t_self;
+ *tid = update_ctid;
*newSlot = epqslot;
goto ltrmark;
}
tuple.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tuple.t_len = ItemIdGetLength(lp);
tuple.t_self = *tid;
+ tuple.t_tableOid = RelationGetRelid(relation);
}
result = heap_copytuple(&tuple);
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.244 2002/10/31 19:25:29 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.244.2.1 2005/08/26 20:07:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
Buffer Cbuf = buf;
bool freeCbuf = false;
bool chain_move_failed = false;
- Page Cpage;
- ItemId Citemid;
ItemPointerData Ctid;
HeapTupleData tp = tuple;
Size tlen = tuple_len;
break; /* out of walk-along-page loop */
}
- vtmove = (VTupleMove) palloc(100 * sizeof(VTupleMoveData));
- num_vtmove = 0;
- free_vtmove = 100;
-
/*
* If this tuple is in the begin/middle of the chain then
- * we have to move to the end of chain.
+ * we have to move to the end of chain. As with any
+ * t_ctid chase, we have to verify that each new tuple
+ * is really the descendant of the tuple we came from.
*/
while (!(tp.t_data->t_infomask & (HEAP_XMAX_INVALID |
HEAP_MARKED_FOR_UPDATE)) &&
!(ItemPointerEquals(&(tp.t_self),
&(tp.t_data->t_ctid))))
{
- Ctid = tp.t_data->t_ctid;
- if (freeCbuf)
- ReleaseBuffer(Cbuf);
- freeCbuf = true;
- Cbuf = ReadBuffer(onerel,
- ItemPointerGetBlockNumber(&Ctid));
- Cpage = BufferGetPage(Cbuf);
- Citemid = PageGetItemId(Cpage,
- ItemPointerGetOffsetNumber(&Ctid));
- if (!ItemIdIsUsed(Citemid))
+ ItemPointerData nextTid;
+ TransactionId priorXmax;
+ Buffer nextBuf;
+ Page nextPage;
+ OffsetNumber nextOffnum;
+ ItemId nextItemid;
+ HeapTupleHeader nextTdata;
+
+ nextTid = tp.t_data->t_ctid;
+ priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
+ /* assume block# is OK (see heap_fetch comments) */
+ nextBuf = ReadBuffer(onerel,
+ ItemPointerGetBlockNumber(&nextTid));
+ nextPage = BufferGetPage(nextBuf);
+ /* If bogus or unused slot, assume tp is end of chain */
+ nextOffnum = ItemPointerGetOffsetNumber(&nextTid);
+ if (nextOffnum < FirstOffsetNumber ||
+ nextOffnum > PageGetMaxOffsetNumber(nextPage))
{
- /*
- * This means that in the middle of chain there
- * was tuple updated by older (than OldestXmin)
- * xaction and this tuple is already deleted by
- * me. Actually, upper part of chain should be
- * removed and seems that this should be handled
- * in scan_heap(), but it's not implemented at the
- * moment and so we just stop shrinking here.
- */
- elog(DEBUG1, "Child itemid in update-chain marked as unused - can't continue repair_frag");
- chain_move_failed = true;
- break; /* out of loop to move to chain end */
+ ReleaseBuffer(nextBuf);
+ break;
}
+ nextItemid = PageGetItemId(nextPage, nextOffnum);
+ if (!ItemIdIsUsed(nextItemid))
+ {
+ ReleaseBuffer(nextBuf);
+ break;
+ }
+ /* if not matching XMIN, assume tp is end of chain */
+ nextTdata = (HeapTupleHeader) PageGetItem(nextPage,
+ nextItemid);
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(nextTdata),
+ priorXmax))
+ {
+ ReleaseBuffer(nextBuf);
+ break;
+ }
+ /* OK, switch our attention to the next tuple in chain */
tp.t_datamcxt = NULL;
- tp.t_data = (HeapTupleHeader) PageGetItem(Cpage, Citemid);
- tp.t_self = Ctid;
- tlen = tp.t_len = ItemIdGetLength(Citemid);
- }
- if (chain_move_failed)
- {
+ tp.t_data = nextTdata;
+ tp.t_self = nextTid;
+ tlen = tp.t_len = ItemIdGetLength(nextItemid);
if (freeCbuf)
ReleaseBuffer(Cbuf);
- pfree(vtmove);
- break; /* out of walk-along-page loop */
+ Cbuf = nextBuf;
+ freeCbuf = true;
}
+ /* Set up workspace for planning the chain move */
+ vtmove = (VTupleMove) palloc(100 * sizeof(VTupleMoveData));
+ num_vtmove = 0;
+ free_vtmove = 100;
+
/*
- * Check if all items in chain can be moved
+ * Now, walk backwards up the chain (towards older tuples)
+ * and check if all items in chain can be moved. We record
+ * all the moves that need to be made in the vtmove array.
*/
for (;;)
{
Buffer Pbuf;
Page Ppage;
ItemId Pitemid;
- HeapTupleData Ptp;
+ HeapTupleHeader PTdata;
VTupleLinkData vtld,
*vtlp;
+ /* Identify a target page to move this tuple to */
if (to_vacpage == NULL ||
!enough_space(to_vacpage, tlen))
{
/* this can't happen since we saw tuple earlier: */
if (!ItemIdIsUsed(Pitemid))
elog(ERROR, "Parent itemid marked as unused");
- Ptp.t_datamcxt = NULL;
- Ptp.t_data = (HeapTupleHeader) PageGetItem(Ppage, Pitemid);
+ PTdata = (HeapTupleHeader) PageGetItem(Ppage, Pitemid);
/* ctid should not have changed since we saved it */
Assert(ItemPointerEquals(&(vtld.new_tid),
- &(Ptp.t_data->t_ctid)));
+ &(PTdata->t_ctid)));
/*
- * Read above about cases when !ItemIdIsUsed(Citemid)
+ * Read above about cases when !ItemIdIsUsed(nextItemid)
* (child item is removed)... Due to the fact that at
* the moment we don't remove unuseful part of
- * update-chain, it's possible to get too old parent
+ * update-chain, it's possible to get non-matching parent
* row here. Like as in the case which caused this
* problem, we stop shrinking here. I could try to
* find real parent row but want not to do it because
* and we are too close to 6.5 release. - vadim
* 06/11/99
*/
- if (!(TransactionIdEquals(HeapTupleHeaderGetXmax(Ptp.t_data),
+ if (!(TransactionIdEquals(HeapTupleHeaderGetXmax(PTdata),
HeapTupleHeaderGetXmin(tp.t_data))))
{
ReleaseBuffer(Pbuf);
chain_move_failed = true;
break; /* out of check-all-items loop */
}
- tp.t_datamcxt = Ptp.t_datamcxt;
- tp.t_data = Ptp.t_data;
+ tp.t_datamcxt = NULL;
+ tp.t_data = PTdata;
tlen = tp.t_len = ItemIdGetLength(Pitemid);
if (freeCbuf)
ReleaseBuffer(Cbuf);
for (ti = 0; ti < num_vtmove; ti++)
{
VacPage destvacpage = vtmove[ti].vacpage;
+ Page Cpage;
+ ItemId Citemid;
/* Get page to move from */
tuple.t_self = vtmove[ti].tid;
InvalidOffsetNumber,
LP_USED);
if (newoff == InvalidOffsetNumber)
- {
elog(PANIC, "moving chain: failed to add item with len = %lu to page %u",
(unsigned long) tuple_len, destvacpage->blkno);
- }
newitemid = PageGetItemId(ToPage, newoff);
+ /* drop temporary copy, and point to the version on the dest page */
pfree(newtup.t_data);
newtup.t_datamcxt = NULL;
newtup.t_data = (HeapTupleHeader) PageGetItem(ToPage, newitemid);
+
ItemPointerSet(&(newtup.t_self), destvacpage->blkno, newoff);
+ /*
+ * Set new tuple's t_ctid pointing to itself for last
+ * tuple in chain, and to next tuple in chain
+ * otherwise.
+ */
+ if (!ItemPointerIsValid(&Ctid))
+ newtup.t_data->t_ctid = newtup.t_self;
+ else
+ newtup.t_data->t_ctid = Ctid;
+ Ctid = newtup.t_self;
+
/* XLOG stuff */
if (!onerel->rd_istemp)
{
if (destvacpage->blkno > last_move_dest_block)
last_move_dest_block = destvacpage->blkno;
- /*
- * Set new tuple's t_ctid pointing to itself for last
- * tuple in chain, and to next tuple in chain
- * otherwise.
- */
- if (!ItemPointerIsValid(&Ctid))
- newtup.t_data->t_ctid = newtup.t_self;
- else
- newtup.t_data->t_ctid = Ctid;
- Ctid = newtup.t_self;
-
num_moved++;
/*
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.180.2.2 2003/03/27 14:33:21 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.180.2.3 2005/08/26 20:07:17 tgl Exp $
*
*-------------------------------------------------------------------------
*/
foreach(l, estate->es_rowMark)
{
execRowMark *erm = lfirst(l);
- Buffer buffer;
HeapTupleData tuple;
+ Buffer buffer;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
TupleTableSlot *newSlot;
int test;
tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
test = heap_mark4update(erm->relation, &tuple, &buffer,
+ &update_ctid, &update_xmax,
estate->es_snapshot->curcid);
ReleaseBuffer(buffer);
switch (test)
case HeapTupleUpdated:
if (XactIsoLevel == XACT_SERIALIZABLE)
elog(ERROR, "Can't serialize access due to concurrent update");
- if (!(ItemPointerEquals(&(tuple.t_self),
- (ItemPointer) DatumGetPointer(datum))))
+ if (!ItemPointerEquals(&update_ctid,
+ &tuple.t_self))
{
- newSlot = EvalPlanQual(estate, erm->rti, &(tuple.t_self));
- if (!(TupIsNull(newSlot)))
+ /* updated, so look at updated version */
+ newSlot = EvalPlanQual(estate,
+ erm->rti,
+ &update_ctid,
+ update_xmax);
+ if (!TupIsNull(newSlot))
{
slot = newSlot;
estate->es_useEvalPlan = true;
{
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
- ItemPointerData ctid;
int result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
/*
* get information on the (current) result relation
*/
ldelete:;
result = heap_delete(resultRelationDesc, tupleid,
- &ctid,
+ &update_ctid, &update_xmax,
estate->es_snapshot->curcid);
switch (result)
{
case HeapTupleUpdated:
if (XactIsoLevel == XACT_SERIALIZABLE)
elog(ERROR, "Can't serialize access due to concurrent update");
- else if (!(ItemPointerEquals(tupleid, &ctid)))
+ else if (!ItemPointerEquals(tupleid, &update_ctid))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- resultRelInfo->ri_RangeTableIndex, &ctid);
+ TupleTableSlot *epqslot;
+ epqslot = EvalPlanQual(estate,
+ resultRelInfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
if (!TupIsNull(epqslot))
{
- *tupleid = ctid;
+ *tupleid = update_ctid;
goto ldelete;
}
}
HeapTuple tuple;
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
- ItemPointerData ctid;
int result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
int numIndices;
/*
* replace the heap tuple
*/
result = heap_update(resultRelationDesc, tupleid, tuple,
- &ctid,
+ &update_ctid, &update_xmax,
estate->es_snapshot->curcid);
switch (result)
{
case HeapTupleUpdated:
if (XactIsoLevel == XACT_SERIALIZABLE)
elog(ERROR, "Can't serialize access due to concurrent update");
- else if (!(ItemPointerEquals(tupleid, &ctid)))
+ else if (!(ItemPointerEquals(tupleid, &update_ctid)))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- resultRelInfo->ri_RangeTableIndex, &ctid);
+ TupleTableSlot *epqslot;
+ epqslot = EvalPlanQual(estate,
+ resultRelInfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
if (!TupIsNull(epqslot))
{
- *tupleid = ctid;
+ *tupleid = update_ctid;
tuple = ExecRemoveJunk(estate->es_junkFilter, epqslot);
slot = ExecStoreTuple(tuple,
estate->es_junkFilter->jf_resultSlot,
* under READ COMMITTED rules.
*
* See backend/executor/README for some info about how this works.
+ *
+ * estate - executor state data
+ * rti - rangetable index of table containing tuple
+ * *tid - t_ctid from the outdated tuple (ie, next updated version)
+ * priorXmax - t_xmax from the outdated tuple
+ *
+ * *tid is also an output parameter: it's modified to hold the TID of the
+ * latest version of the tuple (note this may be changed even on failure)
+ *
+ * Returns a slot containing the new candidate update/delete tuple, or
+ * NULL if we determine we shouldn't process the row.
*/
TupleTableSlot *
-EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
+EvalPlanQual(EState *estate, Index rti,
+ ItemPointer tid, TransactionId priorXmax)
{
evalPlanQual *epq;
EState *epqstate;
{
Buffer buffer;
- if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, false, NULL))
+ if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, true, NULL))
{
- TransactionId xwait = SnapshotDirty->xmax;
+ /*
+ * If xmin isn't what we're expecting, the slot must have been
+ * recycled and reused for an unrelated tuple. This implies
+ * that the latest version of the row was deleted, so we need
+ * do nothing. (Should be safe to examine xmin without getting
+ * buffer's content lock, since xmin never changes in an existing
+ * tuple.)
+ */
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
+ priorXmax))
+ {
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
+ /* otherwise xmin should not be dirty... */
if (TransactionIdIsValid(SnapshotDirty->xmin))
elog(ERROR, "EvalPlanQual: t_xmin is uncommitted ?!");
* If tuple is being updated by other transaction then we have
* to wait for its commit/abort.
*/
- if (TransactionIdIsValid(xwait))
+ if (TransactionIdIsValid(SnapshotDirty->xmax))
{
ReleaseBuffer(buffer);
- XactLockTableWait(xwait);
- continue;
+ XactLockTableWait(SnapshotDirty->xmax);
+ continue; /* loop back to repeat heap_fetch */
}
/*
}
/*
- * Oops! Invalid tuple. Have to check is it updated or deleted.
- * Note that it's possible to get invalid SnapshotDirty->tid if
- * tuple updated by this transaction. Have we to check this ?
+ * If the referenced slot was actually empty, the latest version
+ * of the row must have been deleted, so we need do nothing.
+ */
+ if (tuple.t_data == NULL)
+ {
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
+
+ /*
+ * As above, if xmin isn't what we're expecting, do nothing.
*/
- if (ItemPointerIsValid(&(SnapshotDirty->tid)) &&
- !(ItemPointerEquals(&(tuple.t_self), &(SnapshotDirty->tid))))
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
+ priorXmax))
{
- /* updated, so look at the updated copy */
- tuple.t_self = SnapshotDirty->tid;
- continue;
+ ReleaseBuffer(buffer);
+ return NULL;
}
/*
- * Deleted or updated by this transaction; forget it.
+ * If we get here, the tuple was found but failed SnapshotDirty.
+ * Assuming the xmin is either a committed xact or our own xact
+ * (as it certainly should be if we're trying to modify the tuple),
+ * this must mean that the row was updated or deleted by either
+ * a committed xact or our own xact. If it was deleted, we can
+ * ignore it; if it was updated then chain up to the next version
+ * and repeat the whole test.
+ *
+ * As above, it should be safe to examine xmax and t_ctid without
+ * the buffer content lock, because they can't be changing.
*/
- return NULL;
+ if (ItemPointerEquals(&tuple.t_self, &tuple.t_data->t_ctid))
+ {
+ /* deleted, so forget about it */
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
+
+ /* updated, so look at the updated row */
+ tuple.t_self = tuple.t_data->t_ctid;
+ /* updated row should have xmin matching this xmax */
+ priorXmax = HeapTupleHeaderGetXmax(tuple.t_data);
+ ReleaseBuffer(buffer);
+ /* loop back to fetch next in chain */
}
/*
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.61.2.1 2005/05/07 21:23:24 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.61.2.2 2005/08/26 20:07:17 tgl Exp $
*
*-------------------------------------------------------------------------
*/
HeapTupleHeaderGetXmax(tuple)))
{
/*
- * inserter also deleted it, so it was never visible to anyone
- * else
+ * Inserter also deleted it, so it was never visible to anyone
+ * else. However, we can only remove it early if it's not an
+ * updated tuple; else its parent tuple is linking to it via t_ctid,
+ * and this tuple mustn't go away before the parent does.
*/
- return HEAPTUPLE_DEAD;
+ if (!(tuple->t_infomask & HEAP_UPDATED))
+ return HEAPTUPLE_DEAD;
}
if (!TransactionIdPrecedes(HeapTupleHeaderGetXmax(tuple), OldestXmin))
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: heapam.h,v 1.79 2002/09/04 20:31:36 momjian Exp $
+ * $Id: heapam.h,v 1.79.2.1 2005/08/26 20:07:17 tgl Exp $
*
*-------------------------------------------------------------------------
*/
HeapTuple tuple, Buffer *userbuf, bool keep_buf,
PgStat_Info *pgstat_info);
-extern ItemPointer heap_get_latest_tid(Relation relation, Snapshot snapshot,
+extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
ItemPointer tid);
extern void setLastTid(const ItemPointer tid);
extern Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid);
-extern int heap_delete(Relation relation, ItemPointer tid, ItemPointer ctid,
- CommandId cid);
-extern int heap_update(Relation relation, ItemPointer otid, HeapTuple tup,
- ItemPointer ctid, CommandId cid);
-extern int heap_mark4update(Relation relation, HeapTuple tup,
- Buffer *userbuf, CommandId cid);
+extern int heap_delete(Relation relation, ItemPointer tid,
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid);
+extern int heap_update(Relation relation, ItemPointer otid,
+ HeapTuple newtup,
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid);
+extern int heap_mark4update(Relation relation, HeapTuple tuple,
+ Buffer *buffer, ItemPointer ctid,
+ TransactionId *update_xmax, CommandId cid);
extern Oid simple_heap_insert(Relation relation, HeapTuple tup);
extern void simple_heap_delete(Relation relation, ItemPointer tid);
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: executor.h,v 1.78 2002/09/04 20:31:42 momjian Exp $
+ * $Id: executor.h,v 1.78.2.1 2005/08/26 20:07:17 tgl Exp $
*
*-------------------------------------------------------------------------
*/
extern void ExecConstraints(const char *caller, ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, EState *estate);
extern TupleTableSlot *EvalPlanQual(EState *estate, Index rti,
- ItemPointer tid);
+ ItemPointer tid, TransactionId priorXmax);
/*
* prototypes from functions in execProcnode.c
projects / postgresql / commitdiff